1. Field of the Invention
The present invention relates to a gas sensor including a gas sensor element for detecting the concentration of a gas to be detected and a method of manufacturing a gas sensor.
2. Description of the Related Art
Gas sensors are attached to an inlet system (for example, an intake pipe or an intake manifold) and an exhaust system of an internal combustion engine, such as a diesel engine or a gasoline engine, to monitor the concentration of a specific gas and to control combustion. Gas sensors that are generally used for such control have a structure in which a gas sensor element is held in a metal shell and a rear end portion of the gas sensor element is covered with a metal cover. To facilitate manufacturing and assembly of a gas sensor, a technology of attaching a resin base, instead of a metal cover, to a rear end portion of the metal shell has been developed (Japanese Patent No. 3873390, FIG. 1).
However, in the gas sensor described in Japanese Patent No. 3873390, the base has a flange; the metal shell, which faces the base, has a crimping portion; and the metal shell and the base are connected to each other by crimping the flange to the crimping portion. Therefore, the gas sensor has a problem in that it is difficult to reduce the size of the gas sensor, because the metal shell has a complex structure and the metal shell, including the crimping portion, has a large diameter. Moreover, because the base is in contact with the metal shell, heat of the metal shell is directly transferred to the base and may cause thermal degradation of the base.